The present invention relates to a method and apparatus for packaging crucibles for use in an analytical furnace and to a system for automatically and sequentially supplying crucibles to the furnace and for automatically introducing samples into the furnace and a crucible for the combustion of the samples.
The manufacture of products such as steel require frequent sampling of the metal during its processing to assure the proper content of nitrogen and oxygen, for example. Such samples are typically combusted in crucibles in an analytical furnace. Both the samples, which frequently are pin samples, and the crucibles are typically handled manually by an analyst, requiring a significant amount of labor and time. Also, combustion furnaces reach temperatures as high as 1700° C., requiring care by the operator during the loading and unloading of sample-containing crucibles. With a resistive furnace where graphite crucibles are employed, the manual handling of crucibles results in the analyst having graphite from the crucibles rubbing off on their hands, lab coats, and some of the surrounding area. Thus, with graphite crucibles, the manual crucible handling and sample loading processes can be somewhat dirty in addition to time consuming, and can result in analytical inconsistencies due to contamination.
Efforts have been made to provide automatic loading for at least ceramic crucibles, as represented by U.S. Pat. No. 4,238,450 in which ceramic crucibles are arranged linearly and introduced upwardly into an induction furnace. Also, sample combustion boats have been the subject of auto-loading, as represented by U.S. Pat. No. 5,395,586. Although these systems provide improved handling of ceramic crucibles, the throughput provided by the systems is somewhat limited in terms of the number of crucibles which can be handled per unit time. There remains a need for a system by which crucibles can be prepackaged in bulk to the analytical laboratory, loaded into a crucible delivery assembly where the crucibles are then automatically introduced into the analytical furnace in sequence, and samples, including calibration samples, are automatically introduced into the crucible through the furnace.